Fluid pressure measurement in a cylindrical tube is carried out through the use of invasive and non-invasive devices. Invasive device include elements which protrude into the fluid within the tube. These invasive devices interfere with fluid flow. Conventional non-invasive devices use a plurality of wire strain gauges disposed along axial and tangential directions of the tube. These gages are used to measure the hoop strain around the circumference of the tube and the longitudinal strain in the tube wall. Comparisons are made between the strain gauge measurements to determine fluid pressure in the tube. The use of these devices is limited to use with thin wall tubing because when used with standard sized or thick walled tubing, not enough strain can be sensed to obtain accurate measurement.
Alternatively, a non-invasive device has included a transducer body of a block shape and having a cylinder bore connectable to a piping system for fluid flow therethrough. This transducer body includes a flat milled in one portion of the block to form a thin section between the milled flat and cylinder bore. Strain gages are mounted in a grid formation on the flat and measure changes in strain resulting from the pressure of the fluid within the bore.